Low-Power and Lossy Networks (LLNs) frequently employ communication links which are highly unstable by nature with recurrent link failures and intermittent connectivity. These issues can be further complicated because link qualities (e.g. in terms of delay, reliability, . . . ) are not symmetric. That is, the communication links can be favorable in the upstream direction (e.g., from a node towards a root node), but unusable (or non desirable) with myriad perturbations in the downstream direction (e.g., from a parent node to a child node), and vice-versa. Due to this, downstream traffic could often suffer from low quality of service (QoS), and even failures to deliver, although the path quality in the upstream direction may meet QoS requirements. Note also that some flows may also require symmetrical path characteristics (e.g. the delay in one directions should not exceed the delay in the other direction by more than X %).
This issue becomes even more critical if the node in-question has a high “centrality” in the network (e.g., the node is located along a communication path of many other nodes), and thus is used as transit for many nodes. For example, the overall connection quality in the network may be stable, but a few select nodes with very high centrality may handle a majority of the transit traffic. This can be unfavorable since it places a lot of processing pressure on the centrally-located nodes and leads to network congestion because of the high amount of traffic transiting these regions. It can also make the network very fragile with limited multi-path options at critical times.